1. Field of the Invention
The present invention relates to a printing device and in particular, it relates to a printing device for printing desired designs and/or letters on a printed face of doughnut-like shape, such as a sidewall face of a vehicular tire.
2. Description of the Related Art
The color of many vehicular tires is generally black for the reason that carbon black is compounded into the rubber component of each tire to be used as a reinforcing agent. However, a demand for colorful vehicular tires in addition to the black one has arisen and some reinforcing agents without carbon black have been developed. As a result, it has become possible to produce tires with various kinds of colors. Nevertheless, there is no superior reinforcing agent to the carbon black in terms of manufacturing cost and functional property and this is a principal factor that the colored tires except for the black tires fail to spread.
Therefore, some methods and apparatus have been proposed to apply colorful colors to the black tires by printing rather than coloring the rubber of which the tire itself is made. For example, some methods of and apparatus for printing in full color on the sidewall face of a tire are disclosed in Japanese laid-open patent publication 2010-125,440 (it will hereinafter be referred to as JPA-'440). The apparatus of JPA-'440 is typically provided with an importing section, an inversion section, a printing section, an exporting section, a controlling section for controlling these elements and a print-controlling section to control the printing motion of the printing section. At the stage of the printing section, cleaning of the printed sidewall face of a tire and primer coating are made, and subsequently a printing is conducted by IJP (inkjet) printing equipment. Then, the injected ink is cured and fixed by exposure of UV ramp U at each printing operation. A predetermined print pattern is printed onto a predetermined position of a tire by recognizing the print-registration mark of the tire added beforehand by an identifying camera, by employing the values of predetermined numbers of pulses generated by a ring encoder during the rotation thereof as a starting point for beginning the printing, and by transmitting a print-start signal to cause spouting of ink from each IJP head.
However, because the inkjet printing apparatus described in JPA-'040 is based on the identifying camera for recognizing the print-registration mark and for creating the original signal, it might not be able to properly print when some dirt, dust and the like attach to the lens of the camera. There is also such a problem that the inkjet printing device is comprised of a lot of parts, resulting in suffering from being complicated in its controlling motion. Besides, there is a problem such that the apparatus tends to become large in its size because the apparatus has many sections such as the import section, the inversion section, the printing section and the exporting section, and these sections are mutually interconnected by the chain conveyer for conveyance.
Furthermore, upon printing, the sidewall of a tire is initially forcibly compressed by an upper weight roll for the purpose of surely flattening the compressed sidewall and thereafter, the printing operation is carried out so as to apply printing onto the flattened sidewall of the tire. Nevertheless, there is such a concern that some distortion of the printing might occur after the load applied by the upper weight roll was released and removed, and after the printed sidewall to which the printing was made under application of the compression thereto is recovered to an original state.